@book { DasCRMVorgehensmodell,
    title = "Das CRM-Vorgehensmodell",
    subtitle = "Eine Entwicklung für die Kunden der Siemens Business Services GmbH & Co. OHG",
    author = "Stefan {Arnold}",
    year = "2002",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832457464",
    url = "https://m.diplom.de/document/221209"
}